<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>to top</title>
</head>
<body>
   <div id="app">
      <section class="sec sec-1">page1</section>
      <section class="sec sec-2">page2</section>
      <section class="sec sec-3">page3</section>
      <div class="toTop">^</div>
   </div>
</body>
<script src="./main.js"></script>
</html>